Control system for lift truck



June 30, 1964 J. E. OLSON 3,139,204

CONTROL SYSTEM FOR LIFT TRUCK Filed Nov. 1, 1960 3 Sheets-Sheet 1 SOL I 5 303 23| 223 305 209 205 SOL I In I T Hg 6 T 226 I Fig.

v I I 3o| \CD 229 225 I H 233 223 23| 22' l 205 INV ENT OR. 711 X John E. Olson 6 Buckhorn, Cheatham 8 Blore ATTORNEYS June 30, 1964 J QLSQN 3,139,204

CONTROL SYSTEM FOR LIFT TRUCK Filed Nov. 1, 1960' 5 Sheets-Sheet 2 I INVENTOR. FORWARD R REVERSE John E. Olson BY 1 NEUTRAL/ Buckhorn, Cheafham 8 Blore F /g. 4

j ATTORNEYS June 30, 1964 J. E. OLSON 3,139,204

CONTROL SYSTEM FOR LIFT TRUCK Filed Nov. 1, 1960 3 Sheets-Sheet 3 Fig. 7

d IIVVE/VTOR JOHN E. OLSON BUCKHORN, CHEATHAM 8 BLORE ATTORNEYS United States Patent 3,139,204 CONTROL SYSTEM FOR LIFT TRUCK John E. Olson, Portland, Oreg., assignor to Hyster Company, Portland, Oreg., a corporation of Nevada Filed Nov. 1, 1960, Ser. No. 66,493 '7 Claims. (Cl. 214-650) This invention relates to vacuum type load handling equipment and particularly to an integrated control system for an industrial lift truck having a vacuum type load handling device.

In the prior application of John E. Olson and Donald A. Harris, entitled Vacuum Material Handling Vehicle, Serial No. 842,927, filed September 28, 1959, there is disclosed a lift truck of the general type under consideration having a manually operable control arrangement for controlling the operation of the engine of a (truck to better utilize the engine as a vacuum pump.

It is a main object of the present invention to provide in a lift truck of the suction lift type a series of controls which not only provides for proper operation of the various mechanism of the truck but in addition prevents or precludes mistakes by the operator during load handling operations.

' Another object of the invention is to provide in a vacuum type lift truck a control system which prevents inadvertent release of the load while the truck is being driven from place to place. v

Anotherobje'ct of the invention is to provide in a lift truck a control system which prevents speeding up of the main engine of the truck unless the clutch control member of the truck has been at least partially actuated.

Another object of the invention is to provide an integrated lift truck control system for (1) automatically speeding up the operation of both engines when a load is contacted by the suction device and the clutch control means of the truck engine has been at least partially actuated, (2) cutting out the truck engine after a desired vacuum is attained while leaving the auxiliary pump in control of the vacuum to the suction device, and (3) preventing the load from being released until the suction device has been relieved of the weight of the load and the clutch has been disengaged.

Various other objects will be apparent from the following description taken in connection with the accom panying drawings wherein:

FIG. 1 is a diagrammatic view of a lift truck having a control system of the present invention;

FIG. 2 is-a diagram of the electrical circuit;

FIG. 3 is a side view on an enlarged scale of part of the system in FIG. 1;

FIG. 4 is a sectionalview on an enlarged scale taken along line 44 of FIGJ3; v

' FIG. 5 is a view of a portion of the structure of FIG. 3, taken from the opposite side of the truck;

FIG. 6 shows a modified form of circuit; and,

. FIG. 7 is an enlarged fragmentary view of aportion of FIG. 1 to better show the relationship of certain parts.

General Description Referring to FIG. 1, the truck 5 has a suction type load engagingdevice 6 connected by a conduit 7 to the air filter housing 8 of the internal combustion engine 9 of the truck.- The engine 9 constitutes a source of suction for the device. An auxiliary pump 10 driven by its own engine 11 also constitutes a source of vacuum for the device. I v

An integrated control system is provided for (1) automatically speeding up the operation of both engines when a load is contacted by the suction device and the clutch control meansof the truck engine has been at least partially actuated, (2) cutting out the truck engine after a ice desired vacuum is attained while leaving the auxiliary pump in control of the vacuum to. the suction device, and (3) preventing the load from being released until the suction device has been relieved of the Weight of the load and the clutch has been disengaged.

Specific Description Referring to FIG. 1, the outline 5 indicates a lift truck having a mast 13 pivoted at 15 in conventional fashion on the truck body or on the front axle of the truck. A pair of conventional tilt cylinders, one 17 being shown, are pivotally mounted on the truck body at 19 and have pistons 21 equipped with rods 23 pivotally connected to the mast. A valve 27 on the body controls the flow of fluid from a hydraulic pump 29 on the body to the rod ends of the cylinders through conduits, one 31, being shown, and from such rod ends to a sump 33. When the valve 27 is in its neutral position, fluid is trapped in the rod ends of the cylinders to hold the mast in a desired position.

The suction type load engaging device 6 is guided by the mast 13 for vertical movement, which movement is caused by a conventional lift mechanism, such as a hydraulic hoist cylinder, not shown. It is here pointed out that when a load is supported (held against) the suction device and the device is itself supported by the lift mechanism, a forward moment will be created about the pivots 15, which moment is opposed by the fluid trapped in the rod ends of the cylinders 17. Thus,

passageway member 45. The vacuum pump 10 is connected by a conduit 48 to an outlet 49 of the member 45.

The member is connected to the air filter housing 8 and has a load releasing butterfly valve 121 mounted in an inlet pipe section 123 of the member 45.

A gravity-operated flap valve 131 is mounted to close the upper'end of the member 45 when the differential a two position solenoid valve 205. The valve 205 in the pressure across the valve reaches a sufficiently small value as will enable gravity to close the valve, or when the pressure above the valve is greater than the pressure below the valve. This preventsrapid loss of vacuum when the engine 9 dies. A check valve 132 in line 48 performs a similar function for engine 10.

The housing 8 has an air inlet 135'equipped with a load pick up butterfly valve 137 connected to a linkage L ofthe type shown in the copending application of Olson and Harris previously herein identified.

The housing 8 has the usual air filter element (not shown), and a suitable duct 143 leads from the housing to the carburetor of the engine. The carburetor has a barrel B within the lower part of which is a throttle valve 147 connected to the linkage L.

There is a choke valve 148'above the venturi of the barrel. The carburetor has a float chamber F connected to the barrel, and a duct 153 leads from the barrel to the intake manifold 155 of the internal combustion engine 9. A by-pass conduit 161 connects an extended part of trols the flow of air through the conduit 161 and is nected to the-linkage L. 1

The linkage L is actuated by a piston and cylinder unit 201' (FIG. 1), the operation of whichis controlled by position shown connects the piston and cylinder unit 201 to sump S. In its other position, oil from themain engine oil pump 207, which normally flows to the oil filter,

I labeled FIL.," is connected to the unit 201 to actuate the linkage L and speed up operation of the main engine while closing the load pick up vaive 137 and opening the by-pass valve 163.

The solenoid valve 265 is in a circuit (to be presently described) including a switch 269 (FIG. 3) held normally open by a spring leaf 211 engaged by an arm 213 on the clutch pedal shaft 215. When the pedal217 has been slightly depressed (still Within the range of free pedal movement), the arm 213 retreats from an adjustable stop 218 and from the spring leaf 211 sufficiently to release the switch button to close switch 299. 7

However, closure of switch 2199 alone will not cause actuation of the solenoid valve 205 because the switch is in a'series circuit (FIGS. 1 and 2) with a normally open load contact switch 221, mounted on the suction pick up device 6, a normally closed load releasing switch 223, associated with the clutch pedal 217, and a normally closed vacuum sensing switch 225, mounted on the truck body.

switches 221 and 209 willbe closed to complete a circuit to the battery 226 of the truck to energize the valve 205 and actuate the linkage L.

The purpose of the switch 269 is to make certain that the driverhas his foot on the clutch pedal 217 to enable him to disengage the clutch when the suction device is brought against a load to be picked up and as a consequence the engine 9 automatically speeds up. This precaution prevents forward lurching of the truck at such time.

The auxiliary engine 11 is also controlled by the elec-' trical circuit. Conductors 22? and 231 (FIG. 2) connect a two position solenoid valve 233 in parallel with switches 225 and 265 When switch 221 is open, valve'233 is in the position shown and connects a vacuum actuator 235 by means of a conduit 237 to the intake manifold 155 of the main engine 9 so that the biasing spring 241 of the actuator disposes the throttle linkage 243 of the auxiliary engine 11 in an idling position. When switches 221 and 223 are closed, the valve 233 connects the actuator to the suction device 6 by means of a conduit 245 (which is connected to conduit 7). Unless the spring 241 is opposed by vacuum in the actuator, the actuator will move the linkage 243 to a fast throttle position. As the vacuum varies, the actuator will accordingly vary the throttle position to maintain a desired vacuum.

It is here pointed out that the vacuum sensing switch 225 is connected to the conduit 7. by a conduit 246 (FIG. 1) and is responsive to a predetermined vacuum to open and inactivate the solenoid valve 205 and leave the suction device 6 under the control of the auxiliary pump 10. Thus, after the svw'tch' 225 kicks out,.the auxiliary engine 11 will maintain a predetermined high vacuum at the suction device, automatically speeding up or slowing down in accordance with the manner of actuation of the actuator 235.

The load releasing switch 223 is operated by the clutch pedal 217 during the last increment of downward movement of the pedal. However, provision is made for preventing inadvertent dropping of the load.

Referring to FIGS. 3 to 5 and 7, there is a releasing lever 25 1 fixed to one end of a pivot shaft 253 journaled in a block 255 supported by the floor board 257 of the truck. The lever has a bolt 259 adjustably threaded into 'hold. the valve 121 in the position to which it is moved.

Thus, the driver has to increase the downward pressure on the pedal 217 if he is to overcome spring 265 and open the valve 121.

There is 'a latch for preventing inadvertent release of the load. Referring to FIGS. 3 and 4, the block 255 is provided with a bore 269 receiving a plunger 271 urged by a spring 27 3 to assume an unlatched position, that is, a position clear of an extension 275 on the lever 251 as shown in FIG. 4. The details of the latch assembly will be set forth hereinafter. When the valve 121 is in its closed position, the lever 251 is in its FIGS. 3 and 7 position to enable the plunger 271 to move to a position in the path of travel of the extension 275. However, unless there is pressure in a fluid conduit 277 (FIGS. 4 and'l), which connects the bore 269 to a tilt cylinder 17, the plunger will remain in its inoperative retracted position. Thus, in the process of pickingup a load, the plunger will remain retracted until the load is actually picked up. This means that in the processof picking up a load, the pedal 217 could be fully depressed to open the load releasing valve 121. The only result of this, however, would be to prevent the operator from picking up a load.

Assuming that the operator did fully depress the pedal 217, valve 121 would be thrown open and the spring 265 thrown over center to' tend to hold the valve 121 open. Release of the pedal217 and return of the pedal to its raised position would close the valve 121, because of a pin 279 (FIG. 3) on the lever being engaged by the pedal 217. 7

If for any reason the pedal does not rise far enough to contact the pin 279, the valve 121 may be closed by shiftingthe gear shift lever shaft 281 (FIGS. 4, 5 and 7) of the truck to forward gear. Such movement will pivot the rear portion of lever 251 upwardly through the medium of a chain 283 (FIGS. 5 and 7) which is connected at one Let it be assumed that the truck has been in storage overnight and the drivers first duty is to drive the truck from the storage area to a load a short distance therefrom.

The operator will normally put the truck in reverse from the storage area and then shift into forward gear and move to the loading station. 7 The acts of depressing and releasing the clutch pedal and of shifting into forward gear will automatically warm the control system (close the releasing valve 121) through the medium of the pin 279 or the chain 283.

In approaching the load, the operator will inch the truck up to the load, by appropriate partial'depression of the clutch pedal 217 (which action closes switch 209) and when the load device 6 contacts the load, the switch 221 will be closed. Immediately the operator will depress the clutch pedal 217 until he meets the resistance of the spring 265 at which time he will shift the truck int; 1neutral and cease further depression of the clutch pe a 7 Since switches 223 and 225 are normally closed (FIG. 2) solenoid valve 205 will be energized to cause actuation. of the linkage L. Linkage L will cause the main engine to speed up, by the actuation of the throttle valve 147, and close thevalve 137 (so that the air normally drawn in past the valve 137 will now be drawn from the suction device 6), and open the valve 163.

Because switch 223 is closed, the closure of switch 221 will energize the solenoid valve 233 (FIG. 2) to connect the actuator 235 (FIG. 1) to the suction device 6. The resulting drop in vacuum (increase in pressure) at the vacuum actuator means that'the vacuum actuator spring 241 will move the throttle of'the auxiliary engine to its fast position. Thus, the suction device 6 is connected to two sources of vacuum operating at substantially full capacity.

As soon as a predetermined vacuum is drawn, say 13 inches of mercury, the vacuum sensing switch 225 will open to inactivate the linkage L so that the main engine returns under the control of the engine foot throttle. However, since switches 209 and 223 are still closed, the solenoid valve 233 is still energized and the actuator 235 remains connected to the suction device 6.

Now the operator may lift the suction device 6 by means of the truck hoist cylinder. This action increases the pressure in the tilt cylinders 17 to an extent to actuate the plunger 271 to position it above the lever extension 275 to prevent the clutch pedal 217 from being depressed to an extent to open the load releasing switch 223.

The operator now drives to the load deposit station. During the trip, he is free to shift the truck at will without fear of releasing the load. It will be remembered that shifting into forward gear only acts to close the valve 121, not to open it. Thus, forward shifting has no effect on the valve 121, which is already closed.

A signal light 301 (FIGS. 1 and 2) is provided and may be mounted on the dashboard of the truck. The light is connected in parallel with the switch 209 and thus is affected only by switches 221, 223 and 225. At the time of carrying a load from one place to another, switches 221 and 223 will be closed but switch 225 will be held open by the low pressure at the suction head. However, if for any reason the pressure should rise (vacuum decrease), the switch 225 will close to energize light 301 to warm the driver to stop the truck and find the source of the difiiculty. Thus light 301 serves as a warning to prevent the load from being dropped during transit.

When the operator arrives at the load deposit station, he must relieve the suction device of the weight of the load in order to decrease the pressure in the tilt cylinders 17 so as to cause retraction of the latching plunger 271. As soon as the operator has done this, by lowering the load onto a platform or pallet, he may release the load by fully depressing the pedal 217 to overcome the overcenter spring 265 and open the releasing valve 121. Full depression of the pedal 217 of course causes pivotal move ment of the member 251 and thus causes opening of the switch 223. Opening of switch 223 will prevent the inadvertent speed-up of the main engine and the auxiliary engine at the time of releasing a load. Inadvertent speedup could occur under such circumstances because the switch 221 would very likely be closed and switch 225 would close when the pressure rose, and switch 209 would be closed because the clutch pedal would be depressed.

As the driver backs away from the load and then shifts into forward gear to drive elsewhere, he automatically rearms the control system to condition the control system for picking up another load.

It is pointed out that if during the first pick up operation with a cold engine, the engine tends to die, the oil pressure from the pump 207 will automatically drop and hence release the linkage L to drop the truck back to low throttle normal position.

FIG. 6 shows a modified electrical circuit in which the load contact switch 221 in FIGS. 1 and 2 is replaced by a manually operable switch 22111, which preferably is a push button switch. Switch 221a may be located anywhere within the reach of the driver, such as on the hoist cylinder lever. The switch 221a is connected in parallel with relay contacts 303 and serves to energize a relay coil 305 which actuates the relay contacts 303, the latter being in series with switches 223, 225 and 209.

Thus when a load is engaged by the suction head, it will be necessary for the operator to close switch 221a in order to draw a vacuum at the head. However, momentary closure of switch 221a is all that is required to maintain the contacts closed, because the coil 305 is connected in holding circuit fashion with relation-to relay contacts 303.

In connection with the control system of the present invention, since switch 225 affects solenoid valve 205, but not solenoid valve 233, the switch could be eliminated and a vacuum responsive means could be associated with the solenoid valve 205 to affect the operation of the linkage L in the same manner that switch 225 affects the linkage L.

While the control system of the present invention has been shown in connection with a lift truck having a standard transmission actuated by a clutch pedal, the system could be readily incorporated in a power shift type transmission (hand lever actuated) or by an automatic transmission, such as disclosed in the application of Cecil J. Ross, Jr., filed April 20, 1959, Serial No. 807,512, now US. Patent No. 2,968,967, and entitled Drive System For Lift Truck.

In a power shift transmission, the switch 209 could be eliminated and switch 223 could be associated with the neutral position of the hand lever, while in an automatic transmission of the Ross type, switch 209 could be associated with the inching pedal and the switch 223 operated by a separate control member. The control member would be in an inactive position, at times when the truck was carrying a load in a manner like that shown in the present application for the member 251.

In connection with the form of the invention shown in the drawings, the switch 209 could be arranged so that it is not closed until the clutch pedal was depressed an extent to fully disengage the clutch, and such a construction is contemplated. However, the form shown is preferred.

Clutch Pedal Latch The details of the clutch pedal latch assembly shown in FIG. 4 are as follows. The small bore 269 communicates with a large bore 421, the latter containing a loose piston 423 engaged by the spring 273. The piston has a poppet valve 425 formed thereon for seating against a seat 427, formed on the block 255.

A bleed port 429 is formed in the bore 269. The port is large enough to handle the leakage around the piston and is connected to the sump.

When the pressure in the forward ends of the tilt cylinders increases (because a load is picked up), the pressure in hose 277 increases and despite the leakage around the piston 423, a differential pressure is created across the piston to force the valve 425 to seat against seat 427. This prevents further loss of fluid through the bleed port 429. The port assures that fluid will not be trapped in passage 269 and thus assures good seating of the valve 425. 1

Having described the invention in what is considered to be the preferred embodiment thereof, it is desired that it be understood that the invention is not to be limited other than by the provisions of the following claims.

I claim:

1. In combination, a vehicle having an internal cornbustion engine to drive the vehicle, said engine having an intake manifold and also having clutch control means, a vacuum type load pick up device on said vehicle, and means operable when said clutch control means is at least partially actuated and when an independent control has been actuated to place said device in communication with said intake manifold and to speed up operation of said engine.

2. In combination with a lift truck having an internal combustion engine and a clutch to be disengaged and engaged by a clutch control member, suction type load engaging means on said truck connected to the engine intake manifold, engine accelerating means operable when actuated to cause engine acceleration, and means responsive to predetermined actuation of said clutch control member to actuate said engine accelerating means.

3. In combination with a lift truck having an internal combustion engine to drive said truck through a clutch means controlled by a clutch control means, a suction type load lifting means on said truck, means connecting said suction means to the engine intake manifold, an auxiliary source of vacuum on said truck connected to said suction means, said auxiliary source having an engine of its own, a speed up control, means for (1) automatically speeding up the operation of both engines when said control has been actuated and the clutch control means of the truck engine has been at least partially actuated in a direction toward clutch disengagement, (2) terminating communication of said load lifting means with said intake manifold after a desired vacuum is attained while leaving the auxiliary source in communication with the suction means, (3) preventing the load from being released until the suction means has been relieved of the Weight of the load.

4. In combination with a lift truck having an internal combustion engine to drive said truck through a clutch, a suction type load lifting means on said truck, means connecting said suction means to the engine intake manifold, an auxiliary source of vacuum on said truck connected to said suction means, said auxiliary source having a motor of its oWn, vacuum releasing means, means for (1) speeding up the operation of said engine and said motor when a load is contacted by the suction device and when an additional means has been actuated, (2) termimating the communication of said suction means with said engine manifold after a desired vacuum is, attained while leaving the auxiliary source in control of the supply of vacuum to the suction means, (3) preventing the operation of said vacuum releasing means until the suction means has been relieved of the Weight of the load and the clutch has been disengaged.

5. In combination with a lifttruck having a load lifting mechanism, said lifting mechanism including suction means for engaging a load to be lifted, a source of vacuum for said suction means, means providing an ambient air inlet connected to said suction means, normally closed valve means for controlling the communicationbetween said air inlet and said suction means, means for actuating said valve means, and means for preventing actuating said 8 actuating means anytime the lift mechanism is supporting a load.

6. In combination with a lift truck having (1) suction means for engaging and lifting a load,

(2) variable rate vacuum supply means for said suction means,

(3) means for'placing said suction means in communication with said vacuum supply means and for varying the rate thereof including (a) manually actuated control means operable to return to its unactuated condition after the actuating force is removed,

(12) other means actuated upon actuation of said manually operable means to assume and remain in an actuated condition until deactivatedby other action,

(4) and means operable when actuated for placing said suction means in communication 'with air at higher pressure than at said suction means and for deactivating said other means.

7. In combination With a lift truck having an internal combustion engine to drive said truck,

a suction type load lifting means on said truck,

means connecting said suction means to the engine intake manifold,

an auxiliary source of vacuum on said truck connected to said suction means,

said auxiliary source having a motor of its own,

clutch controlling means for said engine, and control means for elfecting speed-up of both said engine and said motor to increase the vacuum output thereof,

said control means including a plurality of control devices each of which must be in a predetermined condition to enable operation of said control means,

one of said control devices being actuated upon at least partial actuation of said clutch controlling means.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN COMBINATION, A VEHICLE HAVING AN INTERNAL COMBUSTION ENGINE TO DRIVE THE VEHICLE, SAID ENGINE HAVING AN INTAKE MANIFOLD AND ALSO HAVING CLUTCH CONTROL MEANS, A VACUUM TYPE LOAD PICK UP DEVICE ON SAID VEHICLE, AND MEANS OPERABLE WHEN SAID CLUTCH CONTROL MEANS IS AT LEAST PARTIALLY ACTUATED AND WHEN AN INDEPENDENT CONTROL HAS BEEN ACTUATED TO PLACE SAID DEVICE IN COMMUNICATION WITH SAID INTAKE MANIFOLD AND TO SPEED UP OPERATION OF SAID ENGINE. 